"""AT plotting functions"""
from __future__ import annotations
from math import sqrt
import matplotlib.pyplot as plt
import numpy as np
from matplotlib.axes import Axes
from at.constants import clight
from at.lattice import Lattice, axis_
from at.lattice import RFCavity
from at.physics import get_mcf
# Function to compute and plot acceptance
[docs]
def plot_acceptance(ring: Lattice, planes, *args, **kwargs):
# noinspection PyUnresolvedReferences
r"""Plots the acceptance
Computes the acceptance at repfts observation points using
:py:func:`.get_acceptance` and plots the tracked
and survived particles, and the acceptance boundary.
Parameters:
ring: Lattice definition
planes: max. dimension 2, Plane(s) to scan for the acceptance.
Allowed values are: *'x'*, *'xp'*, *'y'*,
*'yp'*, *'dp'*, *'ct'*
Keyword Args:
acceptance (tuple[ndarray, ndarray, ndarray]): tuple containing
pre-computed acceptance *(boundary, survived, grid)*
npoints: (len(planes),) array: number of points in each
dimension
amplitudes: (len(planes),) array: set the search range:
* :py:attr:`GridMode.CARTESIAN/RADIAL <.GridMode.RADIAL>`:
max. amplitude
* :py:attr:`.GridMode.RECURSIVE`: initial step
nturns (int): Number of turns for the tracking
obspt (Refpts): Observation points. Default: start of the machine
dp (float): Static momentum offset
offset: Initial orbit. Default: closed orbit
bounds: Defines the tracked range: range=bounds*amplitude.
It can be used to select quadrants. For example, default values are:
* :py:attr:`.GridMode.CARTESIAN`: ((-1, 1), (0, 1))
* :py:attr:`GridMode.RADIAL/RECURSIVE <.GridMode.RADIAL>`: ((0, 1),
(:math:`\pi`, 0))
grid_mode (GridMode): Defines the evaluation grid:
* :py:attr:`.GridMode.CARTESIAN`: full [:math:`\:x, y\:`] grid
* :py:attr:`.GridMode.RADIAL`: full [:math:`\:r, \theta\:`] grid
* :py:attr:`.GridMode.RECURSIVE`: radial recursive search
use_mp (bool): Use python multiprocessing (:py:func:`.patpass`,
default use :py:func:`.lattice_pass`). In case multiprocessing is not
enabled, *grid_mode* is forced to :py:attr:`.GridMode.RECURSIVE`
(most efficient in single core)
verbose (bool): Print out some information
divider (int): Value of the divider used in
:py:attr:`.GridMode.RECURSIVE` boundary search
shift_zero:
start_method (str): Python multiprocessing start method. The default
:py:obj:`None` uses the python default that is considered safe.
Available parameters: *'fork'*, *'spawn'*, *'forkserver'*.
The default for linux is *'fork'*, the default for macOS and
Windows is *'spawn'*. *'fork'* may be used for macOS to speed up
the calculation or to solve runtime errors, however it is
considered unsafe.
Returns:
boundary: (2,n) array: 2D acceptance
tracked: (2,n) array: Coordinates of tracked particles
survived: (2,n) array: Coordinates of surviving particles
Example:
>>> ring.plot_acceptance(planes, npoints, amplitudes)
>>> plt.show()
"""
obspt = kwargs.pop("obspt", None)
block = kwargs.pop("block", False)
acceptance = kwargs.pop("acceptance", None)
if obspt is not None:
assert np.isscalar(obspt), "Scalar value needed for obspt"
kwargs["refpts"] = obspt
if acceptance is None:
boundary, survived, grid = ring.get_acceptance(planes, *args, **kwargs)
else:
boundary, survived, grid = acceptance
plt.figure()
plt.plot(*grid, ".", label="Tracked particles")
plt.plot(*survived, ".", label="Survived particles")
if len(planes) == 1:
pl0 = axis_(planes[0])
plt.plot(boundary, np.zeros(2), label="Acceptance")
plt.title(f"1D {pl0['label']} acceptance")
plt.xlabel(f"{pl0['label']}{pl0['unit']}")
else:
pl0, pl1 = axis_(planes)
plt.plot(*boundary, label="Acceptance")
plt.title(f"2D {pl0['label']}-{pl1['label']} acceptance")
plt.xlabel(f"{pl0['label']}{pl0['unit']}")
plt.xlabel(f"{pl1['label']}{pl1['unit']}")
plt.legend()
plt.show(block=block)
return boundary, survived, grid
[docs]
def plot_geometry(
ring: Lattice,
start_coordinates: tuple[float, float, float] = (0, 0, 0),
centered: bool = False,
ax: Axes = None,
**kwargs,
):
"""Compute and plot the 2D ring geometry in cartesian coordinates.
Parameters:
ring: Lattice description
start_coordinates: x,y,angle at starting point
centered: it True the coordinates origin is the center of the ring
ax: axes for the plot. If not given, new axes are created
Keyword arguments are forwarded to the underlying
:py:func:`~matplotlib.pyplot.plot` function
Returns:
geomdata: recarray containing, x, y, angle
radius: machine radius
ax: plot axis
Example:
>>> ring.plot_geometry()
"""
if not ax:
fig, ax = plt.subplots()
geom, radius = ring.get_geometry(
start_coordinates=start_coordinates, centered=centered
)
ax.plot(
geom["x"],
geom["y"],
"o:",
linewidth=kwargs.pop("linewidth", 0.5),
markersize=kwargs.pop("markersize", 2),
**kwargs,
)
ax.set_xlabel("x [m]")
ax.set_ylabel("y [m]")
ax.set_aspect("equal", "box")
return geom, radius, ax
[docs]
def plot_sigma(
sigma,
axis: tuple[str, str] = ("x", "xp"),
scale: float = 1.0,
ax: Axes = None,
**kwargs,
):
r"""Plot the projection of the phase space defined by a
:math:`\Sigma`-matrix on the selected plane.
Arguments:
sigma: :math:`\Sigma`-matrix
axis: tuple if indices defining the plane of the :math:`\Sigma`
projection. Allowed values are: *'x'*, *'xp'*, *'y'*,
*'yp'*, *'dp'*, *'ct'*. Default: (*'x'*, *'xp'*)
scale: Scaling factor for the emittance
ax: axes for the plot. If not given, new axes are created
Keyword arguments are forwarded to the underlying
:py:func:`~matplotlib.pyplot.plot` function
"""
if not ax:
fig, ax = plt.subplots()
ax1, ax2 = axis_(axis)
axid = axis_(axis, key="index")
sig22 = sigma[np.ix_(axid, axid)]
eps = sqrt(sig22[0, 0] * sig22[1, 1] - sig22[1, 0] * sig22[0, 1])
sigx = sqrt(sig22[0, 0])
tr = np.array([[sigx, 0.0], [sig22[0, 1] / sigx, eps / sigx]])
loop = 2.0 * np.pi * np.arange(0.0, 1.0, 0.001)
normcoord = np.vstack((np.cos(loop), np.sin(loop)))
coord = tr @ normcoord
line = ax.plot(scale * coord[0, :], scale * coord[1, :], **kwargs)
ax.set_title(f"{ax1['label']}-{ax2['label']} phase space")
ax.set_xlabel(f"{ax1['label']}{ax1['unit']}")
ax.set_ylabel(f"{ax2['label']}{ax2['unit']}")
return line
[docs]
def plot_RF_bucket_hamiltonian(
ring,
ct_range=None,
dp_range=None,
num_points=400,
num_levels=41,
plot_separatrix=True,
**kwargs,
):
r"""Plot the resulting longitudinal Hamiltonian of a ring (defining the RF
bucket). The Hamiltonian is calculated by summing all the cavities in the
ring. Harmonic cavities are supported by the function.
A perfectly tuned lattice is assumed, the cavities' frequency is nominal
and the TimeLag is set in a way ensuring ct=0 for the synchronous phase
by using :py:func:`.set_cavity_phase`.
Parameters:
ring: Lattice description
ct_range (tuple): Forced lower and upper ct values for the plot.
Default to :math:`\pm 1.1 \times C / (2h)`
dp_range (tuple): Forced lower and upper dp values for the plot.
Default to twice the RF acceptance of the bucket.
num_points (int): Number of points for 1D grid (ct/dp)
Default to 400.
num_levels (int): Number of levels for contour plot. Odd number of
levels allow to center the colorbar around 0. Default to 41.
plot_separatrix (bool): Flag to plot the separatrix contour
(:math:`\mathcal{H}=0`).
Returns:
CT: (num_points,num_points) array: ct grid
DP: (num_points,num_points) array: dp grid
hamiltonian: (num_points,num_points) array: Hamiltonian values
along (CT,DP) grid
"""
# Momentum compaction/phase slip factors computed up to third order
tmp_ring = ring.disable_6d(copy=True)
alpha = get_mcf(tmp_ring, fit_order=3, n_step=10)
eta = np.zeros(len(alpha))
eta[0] = alpha[0] - 1 / ring.gamma**2
eta[1] = 3 * ring.beta**2 / 2 / ring.gamma**2 + alpha[1] - alpha[0] * eta[0]
eta[2] = (
-(ring.beta**2) * (5 * ring.beta**2 - 1) / (2 * ring.gamma**2)
+ alpha[2]
- 2 * alpha[0] * alpha[1]
+ alpha[1] / ring.gamma**2
+ alpha[0] ** 2 * eta[0]
- (3 * ring.beta**2 * alpha[0]) / (2 * ring.gamma**2)
)
# (ct, dp) grid calculation (defined around the main RF bucket)
if ct_range is None:
ct = np.linspace(
-0.55 * ring.circumference / ring.harmonic_number,
0.55 * ring.circumference / ring.harmonic_number,
num=num_points,
)
else:
ct = np.linspace(ct_range[0], ct_range[1], num=num_points)
if dp_range is None:
U0 = ring.energy_loss
overvoltage = ring.rf_voltage / U0
rfa = np.sqrt(
2
* U0
/ (np.pi * alpha[0] * ring.harmonic_number * ring.energy)
* (np.sqrt(overvoltage**2 - 1) - np.arccos(1 / overvoltage))
)
dp = np.linspace(-2 * rfa, 2 * rfa, num=num_points)
else:
dp = np.linspace(dp_range[0], dp_range[1], num=num_points)
CT, DP = np.meshgrid(ct, dp)
# Hamiltonian (H=U+T) divided by harmonic number to have
# U = U(V_rf, h, phi_s)
# First term of the Hamiltonian
eta_delta = eta[0] / 2 + eta[1] / 3 * DP + eta[2] / 4 * DP**2
T = ring.beta**2 * ring.energy * eta_delta * DP**2
hamiltonian = T
# Iteration over all lattice cavities
for rfcav in ring[RFCavity]:
Voltage = rfcav.Voltage
HarmNumber = rfcav.HarmNumber
TimeLag = rfcav.TimeLag
phi_s = TimeLag * 2 * np.pi * rfcav.Frequency / ring.beta / clight
phi = (np.pi - phi_s) + CT * 2 * np.pi * rfcav.Frequency / ring.beta / clight
# Second term of the Hamiltonian
U = (
Voltage
/ (2 * np.pi * HarmNumber)
* (np.cos(phi) - np.cos(phi_s) + (phi - phi_s) * np.sin(phi_s))
)
# Add to total Hamiltonian
hamiltonian += U
fig, ax = plt.subplots(1)
lim_range = np.max((np.abs(hamiltonian).min(), np.abs(hamiltonian).max()))
levels = np.linspace(-lim_range, lim_range, num_levels, endpoint=True)
co = ax.contourf(CT, DP, hamiltonian, levels, cmap="coolwarm", alpha=0.7)
# additional contour for visibility
ax.contour(CT, DP, hamiltonian, levels, cmap="coolwarm")
if plot_separatrix:
# separatrix contour
ax.contour(CT, DP, hamiltonian, [0], colors="black")
plt.plot([], [], color="black", label="Separatrix")
ax.legend()
cb = fig.colorbar(co)
cb.set_label(r"$\mathcal{H}(ct,\delta)$ [a.u.]", fontsize=18)
ax.set_xlabel(r"ct [m]")
ax.set_ylabel(r"$\delta$")
phi_s = (
ring.get_rf_timelag()
* 2
* np.pi
* ring.get_revolution_frequency()
* ring.harmonic_number
/ (ring.beta * clight)
)
def ct_to_phi(ct):
return (
np.pi
- phi_s
+ ct
/ (
2
* np.pi
* ring.get_revolution_frequency()
* ring.harmonic_number
/ clight
)
)
def phi_to_ct(phase):
return (
np.pi
- phi_s
- phase
* (
2
* np.pi
* ring.get_revolution_frequency()
* ring.harmonic_number
/ clight
)
)
ax2 = ax.secondary_xaxis("top", functions=(phi_to_ct, ct_to_phi))
ax2.set_xlabel(r"$\phi$ [rad]")
plt.title(r"$\phi_{RF}$ " + rf"= $\pi -$ {phi_s:.2f}", fontsize=18)
return CT, DP, hamiltonian
Lattice.plot_acceptance = plot_acceptance
Lattice.plot_geometry = plot_geometry
Lattice.plot_RF_bucket_hamiltonian = plot_RF_bucket_hamiltonian
